A polybutylene terephthalate resin which is a crystalline thermoplastic resin is excellent in moldability, mechanical strength, electrical property, resistance to heat distortion, and resistance to chemicals, and thus is used as a material of various molded products for the broad purpose of automobiles and electric/electronic equipment.
However, in recent years, a molded product has been complicated in its shape, or provided with thin wall parts in its shape as automobile components, electric/electronic equipment, and the like are minimized. At the time of manufacturing a molded product having such shape, deformation, cracking and the like of the molded product may occur due to a fail in release at the time of molding although the polybutylene terephthalate resin is a material excellent in moldability.
Therefore, a polybutylene terephthalate resin composition that is combined with a mold release agent such as paraffin oil, a fatty acid metal soap, a long chain fatty acid ester, or the like is widely used for the purpose of suppressing occurrence of the fail in release.
The polybutylene terephthalate resin composition that is combined with a mold release agent as described above is described in, for example, Patent Document 1. Specifically, it is described in Examples of Patent Document 1 that combination of the polybutylene terephthalate resin with tetraester of diglycerol having a C18 saturated acyl group (RIKEMAL S-74 manufactured by Riken Vitamin Co., Ltd.) can lower a release force necessary for releasing the molded product from the mold.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2010-189584